Matthew Mannix III, who turned 1 three weeks ago, was pronounced dead about 8:30 a.m. at Mease Countryside Hospital, according to the Pinellas County Sheriff's Office.

Matthew's grandfather saw him in the pool at the home in the 2500 block of Marquis Drive around 7:30 a.m.

Paramedics tried to revive the child. He was then taken by ambulance to the hospital.

According to deputies, Matthew left his crib and open an unlocked bathroom door, which has direct access to the pool deck behind the home. The pool is enclosed by a screen, but there are no barriers around its edge, authorities say.